This invention relates to an automatic sewing machine, more particularly to an automatic sewing machine which cannot only perform normal programmed pattern sewing operations but also work a blank of a cloth clamping member utilized to clamp a piece of cloth being sewed to a movable head by using the same control device utilized to move the head during the normal sewing operation such that not only the pattern configuration of the clamp but also openings provided for the clamp for receiving various pins, for example pin openings utilized to set the position of the cloth when it is mounted on the clamp, and a pin hole utilized to position the needle at the starting point of the sewing operation (origin of the sewing operation) are worked.
Generally, in an automatic sewing machine utilized to automatically sew a number of parts of clothes by mass production technique, a piece of cloth is clamped to a movable head by means of a pair of cloth clamping members and the movable head is moved in the X and Y directions of a rectangular coordinate in accordance with a signal read out from a memory device storing a sewing program and contained in the sewing machine. When sewing a profile including an arbitrary curve such as the collar, cuffs and pocket covers of a shirt, for example, by an automatic sewing machine, a piece of cloth to be sewed is clamped between cloth clamping members which are secured to the movable head.
FIG. 1 is a perspective view showing one example of such automatic sewing machine comprising a head of the sewing machine 13 mounted on a table T, which in turn is supported by a side frame 11.
As shown in FIG. 1A, to the lefthand side wall of the head 13 is slidably mounted a pin 31 which when inserted in an opening QA at the working origin of a cloth clamping member 16 brings a sewing needle immediately above the starting position of the sewing operation. The table T is provided with a rectangular opening 14 through which a movable head 15 including cloth clamping members 16 projects. The movable head 15 is mounted on a carriage 19 to be moved in the direction along guide rods 70 by means of a pulse motor 18 and a piano wire 71. The carriage 19 is moved in the Y direction along guide rods 72 by means of a pulse motor 21 and a piano wire 73. A control device 22 is contained in the side frame 11.
FIG. 2 is a block diagram of a control circuit contained in the control device 22 and utilized to move the movable head 15 in a X-Y plane. The control circuit comprises an address selection switch 51 for setting an address of a memory device 53 corresponding to the starting point of a sewing program and an address counter 52 for designating an address in the memory device 53, the count of the counter 52 increasing with the number of addresses set by the address selection switch 51. In the addresses of the memory device 53 are stored a number of sewing programs corresponding to various sewing patterns or profiles. For example, three programs of the patterns of collars A and B and cuff C, working programs of the openings at respective working origins QC, QA, QC (see FIG. 3) and the program of the pin holes for setting the position of the cloth clamped between the cloth clamping members 16, are stored in addresses 0-50, 51-100 and 101-180 respectively. In this case, the address selection switch 51 sets addresses 0, 51 and 101. X register 54 and Y register 57 are used to set the number of pulses in the X and Y directions stored in the memory device corresponding to respective sewing pitches. The outputs of the X and Y registers are applied to an interpolator 65 which may be linear type because the sewing pitch is about 2 mm in most cases. Gate circuits 55 and 60 are connected to receive pulses sent from the interpolator 65 and representing X and Y directions and signals sent from the memory device 53 and representing forward or rearward direction for applying output pulses .+-.XFP and .+-.YFP to pulse motors 56 and 61 respectively which correspond to pulse motors 18 and 21 shown in FIG. 1. An operation counter 58 is provided to count the number of sewing operations where the direction of sewing of a profile is the same, for example. The sewing operations are made at a definite interval in the X direction. This arrangement decreases the number of addresses of the memory device 53 required to sew a given profile. A control signal generator 62 produces a timing signal supplied to various elements 52, 53, 54, 57 and 58 and gate signals supplied to various gate circuits in response to the clock pulse of a predetermined frequency and generated by a clock pulse generator 63.
The automatic sewing machine shown in FIG. 1 utilizes two clamping members 16 for clamping a piece of cloth 17 to be sewed between them (actually two superposed pieces). FIGS. 3A and 3B show two types A and B of a collar and FIG. 3C a cuff C of a shirt. In the case of A, the outer periphery (shown by heavy lines) of the clamping member represents the sewing pattern and QA an opening at the working origin, whereas in the case of B, a slot shaped sewing pattern 35, an opening at the working origin QB, and pin openings P.sub.1 through P.sub.9 for setting the position of the cloth are formed in the clamping member as shown in FIG. 3B. In the same manner, in the case of sewing a cuff C, the cloth clamping member is provided with a groove 36 corresponding to the profile of the cuff, an opening at the working origin QC and pin openings R.sub.1 through R.sub.8. In each case, dotted lines show the passage of the needle. Before this invention, the sewing patterns of the clamping members A, B and C have been prepared by manual works independently of the sewing machine. Especially, in the cases of B and C, working accuracy of the grooves 35 and 36 is low and the working thereof requires much labour and time. Although the positional relationship between the origins QB and QC and the entire pattern curves including the starting positions of the sewing operation must be accurate, the working of the openings at the working origins and the working of the sewing patterns has not been correctly correlated.
Although it has been proposed to use the same computer control for the normal sewing operation of the sewing machine and the working of the blanks of the cloth clamping members as disclosed in U.S. Pat. No. 3,810,414, this method is not advantageous in that owing to considerably high sewing speeds of the sewing machines, especially those used in mass production scale, it is difficult to work grooves or peripheries of complicated patterns at such high speeds.
According to another prior art method, accurately finished templates were prepared and the clamping members were prepared by profiling the template. This method requires to use an independent profile modeling machine. In order to perform satisfactory sewing operation it is necessary to bring the pattern close as far as possible to sewing profiles shown by dotted lines in FIGS. 3A, 3B and 3C.
In mass production of clothes, it is necessary to prepare and store many types of the clamping members having different patterns for sewing clothes of different size and fashion.